Introduction of mesoporosity in low Si/Al zeolites

ABSTRACT

Compositions and methods for preparing mesoporous materials from low Si/Al ratio zeolites. Such compositions can be prepared by acid wash and/or isomorphic substitution pretreatment of low Si/Al ratio zeolites prior to introduction of mesoporosity.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/911,558 filed Jun. 6, 2013, now U.S. Pat. No. 9,295,980 which is acontinuation of U.S. patent application Ser. No. 12/689,127 filed Jan.18, 2010, now U.S. Pat. No. 8,486,369, which claims benefit to U.S.Provisional Patent Application Ser. No. 61/145,724 filed Jan. 19, 2009,the entire disclosures of which are incorporated herein by reference.

BACKGROUND

1. Field

One or more embodiments of the invention relate to compositions andmethods for preparing mesoporous materials from low Si/Al zeolites.

2. Description of Related Art

Previously, methods have been described to introduce mesoporosity intozeolites, for example, in U.S. Patent Application Publication No.2007/0244347. These zeolites have a high silicon-to-aluminum ratio(“Si/Al”) and low extra-framework content, namely, ultrastable zeolite Y(“USY”) CBV 720 provided by Zeolyst International.

As previously described, this zeolite can be treated in the presence ofa pore forming agent (for example, a surfactant) at a controlled pHunder a set of certain time and temperature conditions to introducemesoporosity into the zeolite. Thereafter, the mesostructured materialcan be treated to remove the pore forming agent (for example bycalcination or chemical extraction).

Zeolites used in fluid catalytic cracking (“FCC”) can have larger unitcell sizes than that of CBV 720 (see Table 1). For example, USY zeoliteCBV 500, also from Zeolyst, may be a more suitable raw material for FCCapplications. Additionally, NH₄Y CBV 300, also from Zeolyst, may besuitable for such uses. As shown in Table 1, USY CBV 500 and NH₄Y CBV300 both have larger unit cell sizes, namely 24.53 Å and 24.70 Å,respectively, than USY CBV 720, namely 24.28 Å.

The CBV 500 zeolite contains a significant amount of extra-frameworkalumina (“EFAL”), due to the leach of some framework alumina (“FA”), asrevealed by a decrease in the unit cell size from parent NaY (see Table1). USY CBV 720, a more stabilized zeolite Y, has a much smaller unitcell size, and a reduced EFAL content, due to an acid wash following asevere stabilization treatment (e.g., steaming). CBV 300 zeolite has alow EFAL content, presumably because it is not subjected to heattreatment.

An EFAL content is the percent total of aluminum that has lowextra-framework alumina. From 0-10% can be considered to be a low EFALcontent whereas an EFAL content from 25-100% can be considered to be ahigh EFAL content.

TABLE 1 Physicochemical Characteristics of Zeolites Provided by ZeolystInt'l NaY NH₄Y USY USY CBV 100 CBV 300 CBV 500 CBV 720 Unit Cell (Å)24.65 24.70 24.53 24.28 EFAL Low Low High Low content Si/Al ratio 2.62.6 5.2 30   (total) Cation Sodium Ammonium Ammonium Proton

When the treatment described in previous patent applications tointroduce mesoporosity in CBV 720 was used to introduce mesoporosity inCBV 500, no appreciable amount of mesoporosity was observed. Inaddition, no major change in the physicochemical characteristic of CBV500 was observed. Similar absences of change were observed for CBV 300and CBV 100 when subjected to the same treatments.

SUMMARY

One embodiment of the present invention concerns a method of forming amaterial comprising at least one mesostructured zeolite. The method ofthis embodiment comprises the steps of: (a) acid washing an initialzeolite with an acid thereby forming an acid-washed zeolite, where theinitial zeolite has a total silicon-to-aluminum ratio (Si/Al) of lessthan 30; and (b) forming at least one mesopore within the acid-washedzeolite thereby forming the mesostructured zeolite.

Another embodiment of the present invention concerns a method of forminga material comprising at least one mesostructured zeolite. The method ofthis embodiment comprises the steps of: (a) acid washing an initialzeolite with an acid thereby forming an acid-washed zeolite, where theinitial zeolite has an average unit cell size of at least 24.40 Å; and(b) forming at least one mesopore within the acid-washed zeolite therebyforming the mesostructured zeolite.

Still another embodiment of the present invention concerns a method offorming a material comprising at least one mesostructured zeolite. Themethod of this embodiment comprises the steps of: (a) providing aninitial zeolite; (b) isomorphically substituting at least a portion ofthe framework aluminum in the initial zeolite with framework silicon tothereby form an isomorphically-substituted zeolite; and (c) forming atleast one mesopore within the isomorphically-substituted zeolite therebyforming the mesostructured zeolite.

Yet another embodiment of the present invention concerns a method offorming a material comprising at least one mesostructured zeolite. Themethod of this embodiment comprises the steps of: (a) acid-washing aninitial zeolite having a low silicon-to-aluminum ratio with an acidthereby forming an acid-washed zeolite; and (b) forming at least onemesopore within the acid-washed zeolite thereby forming themesostructured zeolite.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the present invention are described herein with referenceto the following drawing figures, wherein:

FIG. 1 is a graph depicting nitrogen physisorption isotherms at 77K ofzeolite before (square data points) and after (diamond data points)having been treated with ammonium hexafluorosilicate;

FIG. 2a is a graph depicting nitrogen physisorption isotherms at 77K ofCBV 720 before (diamond data points) and after (square data points)having been treated as described in Example 1;

FIG. 2b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 1;

FIG. 3a is a graph depicting an argon physisorption isotherm at 87K ofCBV 500 after having been treated as described in Example 2;

FIG. 3b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 2;

FIG. 4a is a graph depicting argon physisorption isotherms of CBV 500before (square data points) and after (diamond data points) having beentreated as described in Example 4;

FIG. 4b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 4;

FIG. 5a is a graph depicting argon physisorption isotherms of CBV 500before (square data points) and after (diamond data points) having beentreated as described in Example 5;

FIG. 5b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 5;

FIG. 6a is a graph depicting argon physisorption isotherms of CBV 500before (square data points) and after (diamond data points) having beentreated as described in Example 6;

FIG. 6b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 6;

FIG. 7a is a graph depicting argon physisorption isotherms at 87K of CBV500 before (diamond data points) and after (square data points) havingbeen treated as described in Example 7;

FIG. 7b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 7;

FIG. 8a is a graph depicting argon physisorption isotherms at 87K of CBV500 before (diamond data points) and after (square data points) havingbeen treated as described in Example 8;

FIG. 8b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 8;

FIG. 9a is a graph depicting argon physisorption isotherms at 87K of CBV500 before (square data points) and after (diamond data points) havingbeen treated as described in Example 9;

FIG. 9b is a pore size distribution plot obtained using non-lineardensity functional theory of the material produced in Example 9;

FIG. 10 is a graph depicting an argon physisorption isotherm at 77K ofCBV 300 having been treated as described in Example 10;

FIG. 11a is a TEM micrograph of the material prepared in Example 10; and

FIG. 11b is a TEM micrograph of the material prepared in Example 10.

DETAILED DESCRIPTION

Various embodiments of the present invention concern methods forpreparing a material containing a mesostructured zeolite. In one or moreembodiments, the mesostructured zeolite can be prepared by firstsubjecting an initial zeolite to an acid wash and thereafter forming atleast one mesopore in the resulting acid-washed zeolite. In variousother embodiments, the initial zeolite can be subjected to isomorphicsubstitution so as to replace at least a portion of the initialzeolite's framework aluminum atoms with framework silicon atoms.Thereafter, the isomorphically-substituted zeolite can be subjected toone or more processes for forming at least one mesopore in the zeolite.

As just mentioned, an initial zeolite can be employed as a startingmaterial in preparing a mesostructured zeolite. In one or moreembodiments, the initial zeolite can be a non-mesostructured zeolite. Inother various embodiments, the initial zeolite can be a non-mesoporouszeolite. As used herein, the term “non-mesoporous” shall denote acomposition having a total volume of less than 0.05 cc/g of 20 to 80 Ådiameter mesopores. In one or more embodiments, initial zeolite startingmaterials can have a total 20 to 80 Å diameter mesopore volume of lessthan 0.01 cc/g. Additionally, suitable initial zeolites can have a total1 to 20 Å micropore volume of at least 0.3 cc/g. Furthermore, theinitial zeolite can have an average unit cell size of at least 24.40, atleast 24.45, or at least 24.50 Å.

In various embodiments, the initial zeolite can have a lowsilicon-to-aluminum ratio (“Si/Al”). For example, the initial zeolitecan have an Si/Al ratio of less than 30, less than 25, less than 20,less than 15, or less than 10, taking into consideration the totalamount of aluminum in the zeolite (i.e., both framework andextra-framework aluminum). Additionally, the initial zeolite can have anSi/Al ratio in the range of from about 1 to about 30, in the range offrom about 2 to about 20, or in the range of from 3 to 10. Furthermore,in various embodiments, the initial zeolite can have a high EFALcontent. In one or more embodiments, the initial zeolite can have anEFAL content of at least 25, at least 30, at least 35, or at least 40percent.

The type of zeolite suitable for use as the initial zeolite is notparticularly limited. However, in one or more embodiments, the initialzeolite can be a Y zeolite (a.k.a., faujasite). Additionally, theinitial zeolite can be an ultra-stable Y zeolite (“USY”). Specificexamples of commercially-available Y zeolites suitable for use include,but are not limited to, USY CBV 500 and USY CBV 300, both available fromZeolyst International. Furthermore, the initial zeolite can be fullycrystalline and can have long-range crystallinity.

As noted above, the initial zeolite can be pretreated with an acid washprior to being exposed to the method of mesoporosity incorporation.Without being restricted to any specific theory, it is hypothesized thatthe difficulty of mesoporosity introduction in low Si/Al zeolites can becaused by i) the presence of a relatively high EFAL content thatpartially blocks the incorporation of mesoporosity in the zeolite,and/or ii) the higher Al content in the zeolite framework makes thelocal rearrangement needed to accommodate the pore forming agent in thezeolite more difficult (Si—O—Al bonds are less labile in basic pH thanSi—O—Si bonds). Both properties may contribute to the more difficultintroduction of mesoporosity in low Si/Al zeolites.

In one or more embodiments, the initial zeolite can be acid washed byexposing the zeolite in a solution containing an acid for a certainamount of time and temperature. The acid employed during the acid washcan be any known or hereafter discovered mineral acid, organic acid, ormixtures or two or more thereof. Furthermore, in various embodiments,the acid employed can also be a chelating agent. Additionally, one ormore complexing agents (such as fluoride) can be employed during theacid wash. Specific examples of acids suitable for use in the variousembodiments described herein include, but are not limited to,hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, aceticacid, sulfonic acid, oxalic acid, citric acid,ethylenediaminetetraacetic acid (“EDTA”), and mixtures of two or morethereof. In one or more embodiments, the acid comprises citric acid.When a chelating agent is employed, such chelating agent can also beused to treat the initial zeolite simultaneously with thebelow-described procedures for mesopore incorporation (e.g., thechelating agent can be included in the same reaction medium as the pHcontrolling medium and pore forming agent).

In one or more embodiments, a buffer solution can be employed during theacid wash that uses a weak acid in combination with a weak acid salt togive a constant pH. For example, in one embodiment citric acid can beused with ammonium citrate to produce a constant pH, but other weakacids and weak acid salts can be used.

During the acid wash, the acid can be present in an amount in the rangeof from about 1 to about 10, or in the range of from 1.5 to 4milliequivalents per gram of initial zeolite. Additionally, theacid-containing solution employed for the acid wash can have a pH in therange of from about 1 to about 6. Furthermore, the acid wash can beperformed at a temperature in the range of from about 20 to about 100°C. Moreover, the acid wash can be performed over a time period rangingfrom about 5 minutes to about 12 hours, or in the range of from 30minutes to 2 hours. In one or more embodiments, the initial zeolite isnot steamed prior to acid washing.

In one or more embodiments, following the acid wash, the acid-washedzeolite can be vacuum filtered and washed with water. After the waterwash, the acid-washed zeolite can be filtered again. Any filtering andwashing techniques known or hereafter discovered in the art may beemployed for these steps.

Without being restricted to any particular theory, it appears that acidwashing the initial zeolite opens some Si—O—Al bonds in the zeoliteframework, creating Si—OH and Al—OH terminal groups on the surface ofthe zeolite. This seems to make the acid-washed zeolite more reactiveand therefore the incorporation of mesoporosity easier. Accordingly, inone or more embodiments, the acid-washed zeolite can have fewer Si—O—Albonds in its zeolite framework than the above-described initial zeolite.In various embodiments, the acid-washed zeolite can have at least 0.1,at least 1, at least 5, or at least 10 percent fewer Si—O—Al bonds thanthe initial zeolite. Furthermore, the acid-washed zeolite can have agreater number of Si—OH and/or Al—OH terminal groups than the initialzeolite. In various embodiments, the acid-washed zeolite can have atleast 0.1, at least 1, at least 5, or at least 10 percent more Si—OHand/or Al—OH terminal groups than the initial zeolite.

Furthermore, the resulting acid-washed zeolite can have a decreasedaluminum content. However, in one or more embodiments, the aluminumcontent of the acid-washed zeolite can be maintained in an amountsufficient to preserve the unit cell size of the acid-washed zeolite ata minimum of at least 24.30, 24.35, or 24.40 Å.

In addition or in the alternative to the above-described acid washprocedure, the initial zeolite can subjected to a procedure forisomorphically substituting at least a portion of the initial zeolite'sframework aluminum with framework silicon. In one or more embodiments,such substitution can be accomplished by chemical treatment with anisomorphic substitution agent, such as, for example, ammoniumhexafluorosilicate or silicon tetrachloride. In various embodiments, theisomorphic substitution agent can be in liquid form and/or vapor formduring treatment. This treatment is effective to increase the Si/Alratio without causing significant EFAL, thus allowing greater mesoporeformation in the resulting isomorphically-substituted zeolite. Asevidence of this, FIG. 1 depicts nitrogen physisorption isotherms at 77Kof zeolite before (square data points) and after (diamond data points)having been treated with ammonium hexafluorosilicate. FIG. 1 indicatesan increase in mesopore volume of the isomorphically-substituted zeolitebeginning at approximately 0.3 relative pressure. In one or moreembodiments, the isomorphic substitution of the initial zeolite cancause an increase in the Si/Al ratio of at least 1, at least 5, at least10, at least 20, at least 50, or at least 100 percent.

Various embodiments of the present technology can also include anadditional step of controlled drying of the acid-washed zeolite prior tothe below-described mesopore incorporation. Herein, it is shown thatselective drying allows for further tuning the incorporation ofcontrolled mesoporosity in zeolites while maintaining a desired amountof microporosity. In some embodiments, the amount of microporosity andmesoporosity in low Si/Al zeolites can be controlled during pretreatmentby using different drying conditions following acid wash treatment.

As noted above, it appears that the previously-described acid washingopens some Si—O—Al bonds in the zeolite framework, creating Si—OH andAl—OH terminal groups on the surface of the zeolite. This seems to makethe acid-washed zeolite more reactive and therefore the incorporation ofmesoporosity easier. Though not wishing to be bound by theory, itappears that severe drying conditions (for example, 80° C. overnight,but other drying conditions can be used) manage to condense some of thehydroxyl terminal groups created during the acid treatment therebyeliminating at least some of the added reactivity of the zeolite.Increases in the severity of the drying conditions can allow forincorporating significant mesoporosity, while maintaining a high degreeof microporosity in the zeolite. By increasing the severity of dryingconditions, a higher amount of crystallinity and unit cell size (“UCS”)can be preserved.

In one or more embodiments, the optional drying step can include dryingat a temperature of at least 20, at least 50, or at least 80° C.Additionally, the drying step can be performed at a temperature in therange of from about 20 to about 150° C., in the range of from about 50to about 120° C., or in the range of from 70 to 90° C. Furthermore thedrying step can be performed for a time period of at least 5 minutes, atleast 30 minutes, or at least 1 hour. In other embodiments, the dryingstep can be performed for a time period in the range of from about 5minutes to about 24 hours, in the range of from about 15 minutes toabout 12 hours, or in the range of from 30 minutes to 2 hours.

In still other embodiments, the drying step can be omitted entirely. Inother words, after filtering the acid-washed zeolite, the resulting wetcake can be directly subjected to the below-described mesopore formationprocess.

As mentioned above, the pretreated (e.g., acid-washed and/orisomorphically substituted) initial zeolite can be subjected to amesopore formation process in order to form at least one mesopore in thepretreated initial zeolite. Methods for mesopore incorporationcontemplated by various embodiments of the present technology (e.g.,introduction of mesoporosity in zeolites) can generally include thefollowing steps:

-   -   1. Contacting the pretreated zeolite with a pH controlling        medium in the presence of a pore forming agent under various        time and temperature conditions.    -   2. Filter, wash, and dry the zeolite.    -   3. Remove and/or recover the pore forming agent, for example by        calcination (removal) and/or chemical extraction (recovery).    -   4. The resulting material can also be chemically modified (for        example by ion exchange with rare earths), blended with binders,        matrix, and additives, and shaped (for example, in beads,        pellets, FCC catalysts).

In one or more embodiments, the mesopore formation process can beperformed employing any reagents and under any conditions described inU.S. Published Patent Application No. 2007/0244347, the entiredisclosure of which is incorporated herein by reference. For example,the temperature employed during mesopore formation can range from aboutroom temperature to about 200° C. The time period employed can be in therange of from about 2 hours to about 2 weeks. Furthermore, the pHcontrolling medium can have a pH in the range of from about 9 to about11. In one or more embodiments, the pH controlling medium can comprise abase, such as, for example, ammonium hydroxide. Additionally, the poreforming agent can include a surfactant. When basic conditions areemployed, typically a cationic surfactant can be used, such as acetyltrimethyl ammonium halide (e.g., cetyltrimethyl ammonium bromide(“CTAB”)).

Following the contacting step, the zeolite can be filtered, washed,and/or dried. In one or more embodiments, the zeolite can be filteredvia vacuum filtration and washed with water. Thereafter, the recoveredzeolite can optionally be filtered again and optionally dried.

Following the filter, wash, and drying steps, the zeolite can besubjected to heat treatment or chemical extraction in order to remove orrecover at least a portion of the pore forming agent. In one or moreembodiments, the zeolite can be calcined in nitrogen at a temperature inthe range of from about 500 to about 600° C., and then in air for poreforming agent (e.g., surfactant) removal. The pore forming agent removaltechnique is selected based, for example, on the time needed to removeall of the pore forming agent from the zeolite. The total time periodemployed for heat treatment of the zeolite can be in the range of fromabout 30 minutes to about 24 hours, or in the range of from 1 to 12hours.

The resulting mesostructured zeolite can be a one-phase hybrid singlecrystal having long range crystallinity. In one or more embodiments, themesostructured zeolite can be fully crystalline, and can includemesopore surfaces defining a plurality of mesopores. A cross-sectionalarea of each of the plurality of mesopores can be substantially thesame. In various embodiments, the mesostructured zeolite can have atotal 20 to 80 Å diameter mesopore volume of at least 0.05, 0.1, 0.15,or 0.2 cc/g. Additionally, the mesostructured zeolite can have a total20 to 80 Å diameter mesopore volume in the range of from about 0.05 toabout 0.4, or in the range of from 0.1 to 0.3 cc/g.

As noted above, various techniques described herein can be employed tocontrol or maintain the microporosity of the mesostructured zeolite. Inone or more embodiments, the mesostructured zeolite can have a total 1to 20 Å diameter micropore volume of less than 3.0, less than 2.5, lessthan 2.0, less than 1.5, or less than 1.0 cc/g. Additionally, themesostructured zeolite can have a total 1 to 20 Å diameter microporevolume in the range of from about 0.001 to about 3.0, in the range offrom about 0.01 to about 2.0, or in the range of from 0.05 to 1.0 cc/g.

In one or more embodiments, the mesostructured zeolite can have anaverage unit cell size of at least 24.30, 24.35, or 24.40 Å.

In the present technology, it is contemplated that low Si/Al USYmesostructured zeolites can also be prepared by realuminating high Si/Almesostructured zeolites, such as those described in U.S. PatentApplication Publication Number 2007/0244347 from CBV 720. Any methodsknown or hereafter discovered in the art for aluminating a zeolite canbe employed in this embodiment.

The following examples are intended to be illustrative of the presentinvention in order to teach one of ordinary skill in the art to make anduse the invention and are not intended to limit the scope of theinvention in any way.

EXAMPLES Example 1 No Pretreatment of CBV 720

8 g of CBV 720 were added to a clear solution containing 50 mL ofdeionized water, 15 mL of an NH₄OH aqueous solution (30 wt %), and 4 gof cetyltrimethyl ammonium bromide (“CTAB”) to form a suspension. Thesuspension was treated in a sealed vessel at 80° C. for 24 hrs. Afterthis time, the solid was filtered out, washed with deionized water,dried at room temperature overnight, and heat treated. During heattreatment, the sample was heated in a nitrogen atmosphere from roomtemperature to 550° C. in 4 hours, the sample was held at 550° C. for 2hours, and then dried in air for 8 hours at 550° C.

This treatment produced the incorporation of a significant amount ofmesoporosity (over 0.2 cc/g) with a controlled pore size (2-8 nm). Thesample was tested by nitrogen physisorption at 77K (FIGS. 2a and 2b ).

Example 2 No Pretreatment of CBV 500

8 g of CBV 500 were added to a clear solution containing 50 mL ofdeionized water, 15 mL of an NH₄OH aqueous solution (30 wt %), and 4 gof CTAB to form a suspension. The suspension was treated in a sealedvessel at 80° C. for 24 hrs. After this time, the solid was filteredout, washed with deionized water, dried at room temperature overnight,and heat treated. During heat treatment the sample was heated in anitrogen atmosphere from room temperature to 550° C. in 4 hours, held at550° C. for 2 hours, and then dried in air for 8 hours at 550° C.

This treatment did not produce any significant mesoporosity in the finalmaterial, as tested by argon physisorption at 87K (FIGS. 3a and 3b ).

Example 3 No Pretreatment of CBV 300

8 g of CBV 300 were added to a clear solution containing 50 mL ofdeionized water, 15 mL of an NH₄OH aqueous solution (30 wt %), and 4 gof CTAB to form a suspension. The suspension was treated in a sealedvessel at 80° C. for 24 hrs. After this time, the solid was filteredout, washed with deionized water, dried at room temperature overnight,and heat treated. During heat treatment the sample was heated in anitrogen atmosphere from room temperature to 550° C. in 4 hours, held at550° C. for 2 hours, and then dried in air for 8 hours at 550° C.

This treatment did not produce any significant mesoporosity in the finalmaterial.

Example 4 Acid Wash Pretreatment of CBV 500

25 g of dried CBV 500 were added to a solution containing 750 mLdeionized water containing 6.4 g of citric acid to form a suspension.The suspension was stirred for 30 min. at room temperature. The solidwas vacuum filtered and washed using 750 mL H₂O and the solid wasfiltered again. The filter cake was recovered and dried at 80° C.overnight. Then the solid was sieved and 22.90 g of solid wererecovered.

22.8 g of the recovered, pre-treated CBV 500 solid were added to a clearsolution containing 152 mL deionized water, 46 mL NH₄OH, and 9.1 g ofCTAB to form a suspension. The suspension was treated in a sealed vesselat 80° C. for 24 hrs. Then, the solid was filtered out and the cake waswashed with deionized water (in situ washing 3×300 mL H₂O). The filteredcake was removed and dried in an oven overnight at 80° C. The sample washeated in nitrogen atmosphere at 550° C. for 2 hrs and then heated at600° C. in air for 4 hrs.

This treatment produced a small amount of mesoporosity, while retaininga significant amount of microporosity as tested with argon adsorption(FIGS. 4a and 4b ).

Example 5 Acid Wash Pretreatment of CBV 500

A solution of 25 g citric acid and 750 mL deionized water was prepared.The solution was stirred for 10 min. A first 8.33 g of CBV 500 wereadded to the solution and stirred for 10 min. A second 8.33 g of CBV 500were added to the suspension and was then stirred for an additional 10min. A third 8.33 g of CBV 500 were added to the suspension and was thenstirred for an additional 10 min. Thus, a total of 25 g of CBV 500 werestirred into the citric acid/deionized water solution. Then the totalsuspension was stirred for 1 hr. The suspension was transferred to avacuum filter unit, where it was filtered and washed in situ using 750mL H₂O. The recovery was dried in an oven at 80° C. overnight.

19.88 g of the above solid were added to a clear solution containing 133mL H₂O, 40 mL NH₄OH, and 7.95 g CTAB. The suspension was treated in asealed vessel at 80° C. for 24 hrs. After this time, the solid wasfiltered out and washed with deionized water in situ. The filter cakewas recovered and dried in an oven overnight at 80° C. The sample washeated in nitrogen atmosphere at 550° C. for 2 hrs and then heated at600° C. in air for 4 hrs.

This treatment caused high reduction of zeolite microporosity, but didnot introduce a significant amount of mesoporosity as tested by argonphysisorption (FIGS. 5a and 5b ).

Example 6 Acid Wash Pretreatment of CBV 500

25 g of CBV 500 zeolite were added in 375 mL H₂O containing 8 g citricacid to form a suspension. The suspension was stirred for 30 min. atroom temperature. The solid was vacuum filtered and then washed using375 mL H₂O and then filtered. The filter cake was recovered and dried inan oven at 80° C. for 24 hrs. Then the recovered pre-treated CBV 500solid that was recovered from the filter cake was sieved.

21.86 g of the above solid were added to a clear solution containing 146mL H₂O, 44 mL NH₄OH, and 8.74 g CTAB to form a suspension. Thesuspension was treated in a sealed vessel at 80° C. for 24 hrs. Afterthis time the solid was filtered out and washed with deionized water.The filter cake was recovered and dried in an oven overnight at 80° C.The sample was heated in nitrogen atmosphere at 550° C. for 2 hrs andthen heated at 600° C. under air for 4 hrs.

This treatment caused a small reduction of zeolite microporosity, whileintroducing a reasonable amount of mesoporosity (FIGS. 6a and 6b ).

Example 7 Acid Wash Pretreatment of CBV 500 with 1 Hour Drying at 20° C.

25 g of CBV 500 zeolite were added in 375 mL H₂O containing 9.5 g citricacid to form a suspension. The suspension was stirred for 30 min. atroom temperature. The solid was vacuum filtered and washed using 375 mLH₂O. The filter cake was recovered and dried under air for 1 hr. Thenthe recovered pre-treated CBV 500 solid recovered from the filter cakewas sieved.

25 g of the wet cake were added to a clear solution containing 167 mLH₂O, 50 mL NH₄OH, and 10 g CTAB. The suspension was treated in a sealedvessel at 80° C. for 24 hrs. After this time the solid was filtered outand washed with deionized water. The filter cake was recovered and airdried overnight. The sample was heated in nitrogen atmosphere at 550° C.for 2 hrs and then heated at 600° C. under air for 4 hrs.

This treatment caused high reduction of zeolite microporosity, whileintroducing a significant amount of mesoporosity (FIGS. 7a and 7b ).

Example 8 Acid Wash Pretreatment of CBV 500 with 1 Hour Drying at 80° C.

25 g of CBV 500 zeolite were added in 375 mL H₂O containing 9.5 g citricacid to form a suspension. The suspension was stirred for 30 min. atroom temperature. The solid was vacuum filtered and washed using 375 mLH₂O. The filter cake was recovered and dried at 80° C. for 1 hr. Thenthe recovered pre-treated CBV 500 solid recovered from the filter cakewas sieved.

15.38 g of the wet cake were added to a clear solution containing 102 mLH₂O, 31 mL NH₄OH, and 6.15 g CTAB to form a suspension. The suspensionwas treated in a sealed vessel at 80° C. for 24 hrs. After this time thesolid was filtered out and washed with deionized water. The filter cakewas recovered and dried in an oven overnight at 80° C. The sample washeated in nitrogen atmosphere at 550° C. for 2 hrs and then heated at600° C. under air for 4 hrs.

This treatment caused high retention of zeolite microporosity, whileintroducing a smaller amount of mesoporosity than in the case of Example7 (FIGS. 8a and 8b ).

Example 9 Acid Wash Pretreatment of CBV 500 with 24 Hour Drying at 80°C.

25 g of CBV 500 zeolite were added in 375 mL H₂O containing 8 g citricacid to form a suspension. The suspension was stirred for 30 min. atroom temperature. The solid was vacuum filtered and washed using 375 mLH₂O. The filter cake was recovered and dried in an oven at 80° C. for 24hrs. Then the recovered pre-treated CBV 500 solid recovered from thefilter cake was sieved.

21.86 g of the above solid were added to a clear solution containing 146mL H₂O, 44 mL NH₄OH, and 8.74 g CTAB to form a suspension. Thesuspension was treated in a sealed vessel at 80° C. for 24 hrs. Afterthis time the solid was filtered out and washed with deionized water.The filter cake was recovered and dried in an oven overnight at 80° C.The sample was heated in nitrogen atmosphere at 550° C. for 2 hrs andthen heated at 600° C. under air for 4 hrs.

This treatment caused higher retention of zeolite microporosity, whileintroducing an even smaller amount of mesoporosity than it the case ofExample 8 (FIGS. 9a and 9b ).

Characterization Results for Examples 7-9

Argon adsorption was used in order to characterize the samples ofExamples 7-9 in terms of their pore size distribution. Pore widths lowerthan 20 Å are considered to be microporosity, while pore widths from 20to 80 Å are considered to be mesoporosity introduced by the techniqueherein described. In Table 2, the micro- and mesoporosity as well as thetotal pore volume of the three materials described in Examples 7-9 aregiven. For comparison, the micro- and mesoporosity of the original CBV500 sample are shown. In Table 3, the crystallinity and the UCS of thematerials described in Examples 7-9 are presented.

As shown in Table 2, as the severity of the drying conditions increasesthe amount of microporosity preserved. This is consistent with thetheory of reduction in reactivity of the samples dried at highertemperatures. These conditions can be optimized. Very mild conditions(20° C., 1 h) causes the loss of most of the microporosity (from 0.32 to0.072 cc/g), whereas more severe drying conditions (80° C., 24 h) causesa significant reduction in the mesoporosity introduced (0.222 to 0.110cc/g), with improvement in the microporosity (0.224 compared to 0.072cc/g).

TABLE 2 Micro-, Meso-, and Total Pore Volume for CBV 500 and Examples7-9 Micropore Mesopore Total Pore Drying Volume Volume Volume Sampleconditions (cc/g) <20 Å (cc/g) 20-80 Å (cc/g) CBV 500 — 0.320 negligible0.320 Example 20° C., 0.072 0.222 0.301 #7 1 h Example 80° C., 0.2020.209 0.428 #8 1 h Example 80° C., 0.224 0.110 0.351 #9 24 h

TABLE 3 Crystallinity and Unit Cell Size for CBV 500 and Examples 7-9Sample Drying conditions UCS (Å) Crystallinity, % CBV 500 — 24.552 92.6Example #7 20° C., 1 h — — Example #8 80° C., 1 h 24.423 56.7 Example #9 80° C., 24 h 24.446 71.7

Example 10 Isomorphic Substitution Pretreatment of CBV 300

5 g of NH₄Y zeolite (CBV 300 from Zeolyst International) were added to250 mL of 3M ammonium acetate. To this mixture was added 24.5 mL of 0.4Mammonium hexafluorosilicate solution dropwise for 1 hour while stirring.The resulting solid was vacuum filtered and washed with H₂O.

21.86 g of the wet cake were added to a clear solution containing 146 mLH₂O, 44 mL NH₄OH, and 87.4 g CTAB to form a suspension. The suspensionwas treated in a sealed vessel at 80° C. for 24 hrs. After this time thesolid was filtered out and washed with deionized water. The filter cakewas recovered and dried in an oven overnight at 80° C. The sample washeated in nitrogen atmosphere at 550° C. for 2 hrs and then heated at600° C. under air for 4 hrs.

FIG. 10 is a graph depicting an argon physisorption isotherm at 77K ofthe resulting mesostructured zeolite. As can be seen in FIG. 10, themesostructured zeolite displays an increased mesopore volume beginningat approximately 0.3 relative pressure.

FIGS. 11a and 11b are TEM micrographs of the material prepared in thisExample.

Selected Definitions

It should be understood that the following is not intended to be anexclusive list of defined terms. Other definitions may be provided inthe foregoing description accompanying the use of a defined term incontext.

As used herein, the terms “a,” “an,” and “the” mean one or more.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the terms “containing,” “contains,” and “contain” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

As used herein, the terms “having,” “has,” and “have” have the sameopen-ended meaning as “comprising,” “comprises,” and “comprise” providedabove.

As used herein, the terms, “including,” “include,” and “included” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

Unless otherwise indicated, the term “mesoporous” is art-recognized andrefers to a porous material comprising pores with an intermediate size,ranging anywhere from about 2 to about 50 nanometers.

The term “mesostructure” is art-recognized and refers to a structurecomprising mesopores which control the architecture of the material atthe mesoscopic or nanometer scale, including ordered and non-orderedmesostructured materials, as well as nanostructured materials, i.e.,materials in which at least one of their dimensions is in the nanometersize range, such as nanotubes, nanorings, nanorods, nanowires,nanoslabs, and the like.

The term “mesostructured zeolites” as used herein includes allcrystalline mesoporous materials, such as zeolites, aluminophosphates,gallophosphates, zincophosphates, titanophosphates, etc. Itsmesostructure maybe in the form of ordered mesporosity (as in, forexample MCM-41, MCM-48 or SBA-15), non-ordered mesoporosity (as inmesocellular foams (MCF)), or mesoscale morphology (as in nanorods andnanotubes). The notation zeolite[mesostructure] is used to designate thedifferent types of mesostructured zeolites.

“Y” represents a faujasite which is a zeolite comprising 2 moles ofsodium and 1 mole of calcium in its octahedral crystal structure. Thisterm also includes the acidic form of Y which may also be represented as“H—Y.”

The term “zeolite” is defined as in the International ZeoliteAssociation Constitution (Section 1.3) to include both natural andsynthetic zeolites as well as molecular sieves and other microporous andmesoporous materials having related properties and/or structures. Theterm “zeolite” also refers to a group, or any member of a group, ofstructured aluminosilicate minerals comprising cations such as sodiumand calcium or, less commonly, barium, beryllium, lithium, potassium,magnesium and strontium; characterized by the ratio(Al+Si):O=approximately 1:2, an open tetrahedral framework structurecapable of ion exchange, and loosely held water molecules that allowreversible dehydration. The term “zeolite” also includes“zeolite-related materials” or “zeotypes” which are prepared byreplacing Si.sup.4+ or Al.sup.3+ with other elements as in the case ofaluminophosphates (e.g., MeAPO, SAPO, ElAPO, MeAPSO, and ElAPSO),gallophosphates, zincophophates, titanosilicates, etc.

What is claimed is:
 1. A method of forming a material comprising atleast one mesoporous zeolite, said method comprising the steps of: (a)acid washing a non-mesoporous initial zeolite with an acidic mediumthereby forming an acid-washed zeolite, wherein said initial zeolite hasa total silicon-to-aluminum (Si/Al) ratio of less than 30, wherein saidacid washing of step (a) removes aluminum atoms from said initialzeolite such that said acid-washed zeolite has a higher Si/Al ratio thansaid initial zeolite; (b) recovering said acid-washed zeolite from saidacidic medium thereby forming a recovered zeolite; and (c) contactingsaid recovered zeolite with a mesopore-forming medium thereby forming atleast one mesopore within said recovered zeolite and providing saidmesoporous zeolite.
 2. The method of claim 1, wherein said recovering ofstep (b) involves washing, filtering, drying, or a combination thereof.3. The method of claim 1, wherein said initial zeolite has a Si/Al ofless than
 10. 4. The method of claim 1, wherein said acidic medium doesnot comprise hydrofluoric acid.
 5. The method of claim 1, wherein saidacidic medium comprises at least one acid selected from the groupconsisting of chlorhidric acid, sulphuric acid, nitric acid, aceticacid, sulfonic acid, oxalic acid, ethylenediaminetetraacetic acid(EDTA), citric acid, and combinations thereof.
 6. The method of claim 1,wherein said initial zeolite has a total 20 to 80 Å diameter mesoporevolume of less than 0.05 cc/g, wherein said mesoporous zeolite has atotal 20 to 80 Å diameter mesopore volume of at least 0.1 cc/g.
 7. Themethod of claim 1, wherein said initial zeolite has an average unit cellsize of at least 24.40 Å and said acid-washed zeolite has an averageunit cell size of at least 24.35 Å.
 8. The method of claim 1, whereinsaid mesoporous zeolite is a mesostructured zeolite, a one-phase hybridsingle crystal having long-range crystallinity.
 9. The method of claim1, wherein said acid washing is performed at a temperature of not morethan 100° C., wherein said acid washing is performed for a time periodof not more than 12 hours.
 10. The method of claim 1, wherein saidacidic medium comprises an acid that is present in an amount in therange of from about 1 to about 10 milliequivalents per gram of initialzeolite.
 11. The method of claim 1, wherein said acidic medium comprisesa chelating agent selected from the group consisting of oxalic acid,citric acid, and ethylenediaminetetraacetic acid (EDTA).
 12. The methodof claim 1, wherein said acidic medium is in liquid form during saidacid-washing.
 13. The method of claim 1, wherein said mesopore-formingmedium comprises a base.
 14. The method of claim 13, wherein saidmesopore-forming medium comprises at least one surfactant.
 15. Themethod of claim 13, wherein said base comprises ammonium hydroxide. 16.The method of claim 14, wherein said surfactant comprises cetyltrimethylammonium halide.
 17. The method of claim 1, wherein said initial zeolitehas an extra-framework aluminum content of 25% to 100%.
 18. The methodof claim 1, further comprising recovering said mesoporous zeolite fromsaid mesopore-forming medium, wherein said recovering involves washing,filtering, drying, or a combination thereof.
 19. The method of claim 1,wherein said initial zeolite comprises a faujasite.
 20. The method ofclaim 1, further comprising blending said mesoporous zeolite with abinder, a matrix, and/or an additive to thereby form a blended material,further comprising shaping said blended material into a catalystcomposition.